Kerbal Space Program

''Kerbal Space Program'' (''KSP'') is a space flight simulation video game developed by Mexican developer Squad for Microsoft Windows, macOS, Linux, PlayStation 4, and Xbox One. In the game, players direct a nascent space program, staffed and crewed by green humanoid aliens known as "Kerbals". The game features a realistic orbital physics engine, allowing for various real-life orbital maneuvers such as Hohmann transfer orbits and orbital rendezvous.

The first public version was released digitally on Squad's ''Kerbal Space Program'' storefront on 24 June 2011, and joined Steam's early access program on 20 March 2013. The game was released out of beta on 27 April 2015. ''Kerbal Space Program'' has support for user-created mods that add new features. Popular mods have received support and inclusion in the game by Squad. People such as Scott Manley and organizations involved in space travel have taken an interest in the game, including NASA, the European Space Agency, United Launch Alliance CEO Tory Bruno, CEO and CTO of SpaceX Elon Musk and Peter Beck, CEO and CTO of Rocket Lab.

In May 2017, Squad announced that the game had been purchased by video game company Take-Two Interactive, who will help support Squad in keeping the console versions up-to-date alongside the personal computer versions. An ''Enhanced Edition'' was released for Xbox One and PlayStation 4 in January 2018, and for PlayStation 5 and Xbox Series X/S in September 2021 by Private Division, a publishing subsidiary of Take-Two Interactive. Two expansions for the game have been released as downloadable content: ''Making History'' in March 2018 and ''Breaking Ground'' in May 2019. A sequel, ''Kerbal Space Program 2'', is scheduled for release on February 24, 2023.

Gameplay

The player administers a space program operated by Kerbals, a species of small green humanoids, who have constructed a spaceport called the Kerbal Space Center (KSC) on their home planet, Kerbin. From this space center players can create rockets, aircraft, spaceplanes, rovers, and other craft from a provided set of components. Once built, the craft can be launched by players from the KSC launch pad or runway in an attempt to complete player-set or game-directed missions while avoiding partial or catastrophic failure (such as lack of fuel or structural failure). Players control their spacecraft in three dimensions with little assistance other than a Stability Assist System (SAS) to keep their rocket oriented. Provided it maintains sufficient thrust and fuel, a spacecraft can enter orbit or even travel to other celestial bodies. To visualize vehicle trajectory, the player must switch into map mode; this displays the orbit or trajectory of the player vehicle, as well as the position and trajectory of other spacecraft and planetary bodies. These planets and other vehicles can be targeted to view information needed for rendezvous and docking, such as ascending and descending nodes, target direction, and relative velocity to the target. While in map mode, players can also access maneuver nodes to plan out trajectory changes in advance, which helps in accurately planning burns.

Missions (either player-set or assigned "contracts") involve goals such as reaching a certain altitude, escaping the atmosphere, reaching a stable orbit, landing on a certain planetary body, rescuing stranded Kerbals, capturing asteroids, and creating space stations and surface bases. Players may also set challenges for each other on the game's forums, such as visiting all five moons of Jool (the in-game analog for Jupiter), or use mods to test each other's spacecraft in air combat tournaments.

Players can control in-game astronauts, known as Kerbals, who can perform extravehicular activities (EVA). While on EVA, Kerbals may use their EVA suit propellant system to maneuver in space and around craft and space stations, similar to the use of NASA's Manned Maneuvering Unit. Actions that can be performed while on EVA include repairing landing legs, wheels, and deploying or repacking parachutes. Kerbals can also collect material from science experiments, allowing them to store data inside the ship's capsule. During an EVA on any solid planet or moon, a Kerbal can place a flag or take a surface sample.

Historical spacecraft can be recreated and their accomplishments mimicked, such as the Apollo program, the Mars Science Laboratory rover, or the International Space Station. Various parts in the game are based off of real life parts, such as the Mk1-3 Command Pod being very similar to the Apollo command and service module, and Probodobodyne Stayputnik being similar in name, function, and shape to the Soviet probe Sputnik. Players may install mods which implement destinations, weapons, additional rocket parts, and goals, such as attempting challenges in a real-scale solar system. Mods can also add informational displays showing craft and orbital statistics such as delta-v and orbital inclination, while a few can near-fully automate flight. Some mods have been added into the game, due to popularity. For example, resource mining, to get ore for refining into fuel, has been implemented from a popular mod.

The major celestial bodies in the game in order of their proximity to the parent star, the Sun, are Moho, Eve, Kerbin, Duna, Dres, Jool, and Eeloo (respectively analogs of Mercury, Venus, Earth, Mars, Ceres, Jupiter, and Pluto). Community modifications are able to expand this planetary system, even being able to add exoplanets or other solar systems. Moons in the system include Gilly, a captured asteroid around Eve; the Mun and Minmus, the two moons of Kerbin; Ike, the single moon of Duna; and the five moons of Jool, which include Laythe, an ocean moon dotted with islands; Vall, an ice moon; Tylo, a large Kerbin-sized moon; and Bop and Pol, the two outermost captured asteroids. Laythe is the only moon to have an atmosphere or liquid water. Moho, Dres, and Eeloo do not possess moons.

Game modes

The player starts a new game by choosing one of three game modes: sandbox, science, and career mode. In sandbox mode, players may attempt to construct a suitable vehicle for any desired project without penalties for failure and entirely user-assigned missions. Many players have constructed unrealistic spacecraft in this mode, such as impractically large, complicated, or expensive rockets. This mode is also frequently used to create replicas of real-life vehicles.

In science mode, the initial selection of parts is limited. More complex parts can be unlocked in the Research and Development building by advancing "science" with various experiments on Kerbin and elsewhere throughout the solar system. This mode was designed to ease new players into the game and prevent them from getting overwhelmed.

Career mode extends science mode by adding funds, reputation, and contracts. To build and launch new rockets, the players must complete contracts, earning funds to pay for the necessary parts and fuel. Reputation affects how many contracts are given to the player; less reputation leads to fewer, lower-quality contracts. Declining a contract will reduce the likelihood that a contract of the same type will appear later while also decreasing reputation. Players must upgrade buildings in the space center to unlock new features such as improved tracking, higher spacecraft mass limit, larger part count limit, and increased available contracts.

Physics

While the game is not a perfect simulation of reality, it has been praised for its accurate orbital mechanics; all objects in the game except the celestial bodies are simulated using Newtonian dynamics. For instance, rocket thrust is applied to a vehicle's frame based on the placement of force-generating elements, and joints between parts have limited strength, allowing vehicles to be torn apart by excessive or misdirected forces.

The game simulates trajectories and orbits using patched conic approximation instead of a full n-body simulation; thus, it does not support Lagrange points, perturbations, Lissajous orbits, halo orbits or tidal forces. According to the developers, implementing full n-body physics would require the entire physics engine to be rewritten.

The in-game astronauts, Kerbals, are physically simulated. Hitting an object with their feet will cause them to tumble.

Some celestial bodies have atmospheres of varying heights and densities, affecting the impact of drag on wings and parachutes. The simulations are accurate enough that real-world techniques such as aerobraking are viable methods of navigating the solar system. Aerobraking, however, has become a much more difficult method of velocity reduction since the full 1.0 release due to improved aerodynamics and optional heating during atmospheric entry. In-game atmospheres thin out into space but have finite heights, unlike real atmospheres.

''Kerbal Space Program'' alters the scale of its solar system for gameplay purposes. For example, Kerbin (the game's analog of Earth) has a radius of only , approximately that of Earth's. To compensate for the gravitational consequences of this size difference, Kerbin's density is over 10 times that of Earth's. The planets themselves are also significantly closer together than the planets in the real-life Solar System. However, some mods port the real-world solar system into the game with accurate scaling, environments, and additional parts to make up for the extra power requirements.

Expansions

There are two downloadable content (DLC) expansions: ''Making History'' and ''Breaking Ground''.

;''Making History''
The ''Making History'' expansion, released March 2018, adds additional elements to the game, some of which are historic parts from the Apollo program. These include a lunar lander, basic rocket parts of the Saturn V and more. A level editor allows the players to create their own scenarios. New launch sites, including an island, are added. There are also new suits added that referenced the USSR's cosmonaut program.

;''Breaking Ground''
''Breaking Ground'', released May 2019, adds robotic parts, which can be used to build helicopters, propeller airplanes, suspension systems, and robots. The parts include pistons, hinges and rotors. New suits were added as well. A major addition are surface features and science. The player can find certain rocks on surfaces of planets and analyze them using robotic arms. Science experiments such as active seismometers and weather stations can be deployed by the Kerbals and can be used to gather extra science points in science and career mode.

Development

Pre-development

Director Felipe Falanghe was hired by Squad in April 2010. At the time, the company did not develop software. According to Falanghe, the name "Kerbal" came from the names he gave small tin figurines he installed in modified fireworks as a teenager. In October 2010, development on ''Kerbal Space Program'' was authorized by co-founder Adrian Goya but deferred until Falanghe had completed his projects. ''Kerbal Space Program'' was first compiled on 17 January 2011. The game's first public release, version 0.7.3, was on 24 June 2011. The game entered beta on 14 December 2014, with version 0.90, and was released out of beta on 27 April 2015.

Alpha

Version 0.7.3 was the first public release of ''Kerbal Space Program'', and was released on 24 June 2011. It was downloaded over 5,000 times. Compared to future versions of this game, 0.7.3 was quite rudimentary. There was no stability assist mode, Kerbin did not rotate and the Sun was simply a directional light source. There were no fuel flow mechanics, no control surfaces, and no other celestial bodies. Later versions added additional planets and moons, as well as the ability to load and save collections of parts, known as "subassemblies". Tutorials were also added at this stage.

Version 0.24, titled ''First Contract'' and released on 17 July 2014, added the contracts and reputation system to the game's career mode; however, players were still able to play career mode without these features in the new science mode. Contracts reward the player with currency and reputation. Funds can be used to purchase rocket parts, and reputation results in better and more lucrative contracts.

The final alpha release, 0.25, included a new economic system, and a major rework of aircraft components.

Beta

Version 0.90, nicknamed ''Beta Than Ever,'' was released on 15 December 2014. This was the only beta update for ''Kerbal Space Program''. Featuring extensively rewritten code for the editor, it introduced the ability to sort parts by several characteristics and to assign parts to custom categories. Players could now offset parts, including into space. Career mode featured building upgrades; only the creation of small rockets with low mass and a part count is initially supported, but the player can upgrade each of the facilities to increase size limitations or unlock other capabilities.

Release

Version 1.0 was the first full release of ''Kerbal Space Program''. It was nicknamed ''We Have Liftoff!'' and released on 27 April 2015. Version 1.0 completely overhauled the flight and drag model for a more realistic simulation, now ignoring drag on rocket parts which were occluded from the air flow. It also allowed for body lift, so that parts that were not specifically designed as wings (such as structural panels) could still generate lift. 1.0 added shock heating and heat shields, making atmospheric entry much more dangerous, as well as air brakes and procedurally generated fairings. All parts received internal modeling. Resource mining was added to refine into fuel or monopropellant. 1.0 also brought several improvements to Kerbals, who could now have various specializations. For example, "Engineer" Kerbals can repair wheels and landing legs. Female Kerbals were also added to the game. Version 1.1, nicknamed ''Turbo Charged'', was released on 19 April 2016, almost one year after the last major update. The game engine was upgraded from Unity 4 to Unity 5, resulting in an increase in performance, as well as a stable 64-bit client, removing memory constraints caused by too many mods being installed. Much of the game was rewritten to accomplish this.

Squad released Version 1.2, nicknamed ''Loud And Clear'', to upgrade the game from Unity 5 to 5.4 and introduce performance and minor gameplay improvements. The patch entered experimental testing on 6 September 2016 and was officially released on 11 October 2016. Its main new features include communication satellites, relay systems, and KerbNet. Several updates have been released since.

On 10 June 2021, Squad announced that update 1.12 ''On Final Approach'', would be the last major planned release and that the Squad developers would join the Intercept Games team working on KSP 2.

Other updates, Take-Two Interactive ownership

On 27 January 2014, it was revealed that Squad was working on an education-themed version of the game entitled ''KerbalEdu'' in collaboration with TeacherGaming LLC, creators of '' MinecraftEdu''. It has since been released and includes an improved user interface for easier data gathering and summary, pre-made lessons that focus on certain constructions, options to use the metric system, and a "robust pedagogy" that includes information outside of the game that ties into its content.

Squad has also made an Asteroid Mission Pack, with full support from NASA. Released on 1 April 2014, it is based on the real-life initiative to send humans out to study asteroids.

The majority of the game's music was provided by royalty-free composer Kevin MacLeod, with the rest of the soundtrack having been written by Squad's in-house composer Victor Machado. The game's main theme was composed by lead designer Felipe Falanghe and arranged by Machado.

On 5 June 2015, it was announced that ''Kerbal Space Program'' was being ported to the PlayStation 4 by Flying Tiger Entertainment. In August 2015, it was announced that Xbox One and Wii U ports were also in development by Flying Tiger Entertainment.

The game has since been released on the PlayStation 4 and Xbox One, but Squad has been quiet regarding the announced Wii U port. In January 2017, one of Squad's developers had finally broke the silence on the official forums, and admitted that despite initial enthusiasm to release the game on the Wii U, they claimed that various "external factors" has forced them to reevaluate supporting the console. They added that additional details will be announced at a later date.

On 17 March 2017, Squad announced a full expansion for the game; called ''Making History'', it would be paid and contain new features. These new features included Mission Builder, which would allow players to create and edit their missions that players could complete by launching and operating various rockets and ships in the game, and History Pack, which would provide designed missions simulating important historical space endeavors that have been completed in real life. Squad announced on 7 February 2018 that the expansion would be released on 13 March 2018. The expansion contains many parts inspired by those used in various rockets such as the Soyuz spacecraft and the Saturn V.

Squad announced in May 2017 that ''Kerbal Space Program'' has been acquired by publisher Take-Two Interactive; this acquisition does not affect Squad's development or plans for the game and early backers will still get free DLC, and with Take-Two's help as a publisher, better support ''Kerbal Space Program'' on consoles to keep those versions to-date alongside the PC version. ''Kerbal Space Program'' will be one of the first titles published under Take-Two Interactives's 2017-launched Private Division, a publishing label aimed to support mid-sized development studios.

In late May 2019, Squad released the ''Breaking Ground'' expansion, which includes servos, pistons, new and redesigned space suits, and experiments which can be deployed to earn science over time.

On 24 June 2021, the last version of Kerbal Space Program, version 1.12, was released. It was named "On Final Approach".

Reception

The public alpha and beta releases were well-received. Many publications have spoken positively of the game, praising its replay value and creative aspects, including '' Kotaku'', '' Rock, Paper, Shotgun'', '' IGN'', '' GameSpy'', ''Eurogamer'', ''Polygon'', and ''Destructoid''.

In May 2015, PC Gamer awarded ''Kerbal Space Program 1.0'' a score of 96 out of 100, their highest review score of 2015. They praised the "perfect blend of science and slapstick", as well as the sense of accomplishment felt upon reaching other planets and completing goals. IGN has praised ''Kerbal Space Program'' ability to create fun out of failure, saying that "By the time I finally built a rocket that achieved successful orbit, I had failed so many times that in almost any other game I would have given up completely."

In their review, ''Edge'' thought that "The magic of ''Kerbal Space Program'' is not just that it manages to be both a game and a simulation, a high-level educational tool and something that is fun to simply sit and tinker with. It's that, in combination, these qualities allow for a connection with real history and real human achievement... Its ultimate promise to the player is not that you'll crack a puzzle that has been set by a designer, but that you'll crack a puzzle set by ''reality''."

Commercial

In the hours after its Steam early access release on 20 March 2013, ''Kerbal Space Program'' was one of the platform's top 5 best-selling games, as well as the best seller on Steam for Linux.

Squad has released physical merchandise such as clothing and plush toys. In March 2015, Squad and 3D printing service Eucl3D announced a partnership that would allow players to order 3D printed models of their craft.

Scientific community

The game has crossed over into the scientific community with scientists and members of the space industry displaying an interest in the game, including NASA, ESA, ULA's Tory Bruno, and SpaceX's Elon Musk. Squad has added a NASA-based Asteroid Redirect Mission pack to the game, allowing players in game to track and capture asteroids for mining and study. Squad has also developed an official mod for the game centered around observing and tracking threatening asteroids, named "Asteroid Day". The mod was developed in partnership with the B612 Foundation. Some parts from this mod outside of core functionality were added as part of the release of the 1.1 update, with full integration of the mod to stock game being the version 1.3. In collaboration with ESA, Squad added the BepiColombo and Rosetta missions along with several ESA-themed textures for in-game parts in version 1.10.

For the second orbital test flight of the Boeing Starliner which docked with the International Space Station in May 2022, the crew brought a Kerbal plush on the vessel to be used as the zero gravity indicator. A Boeing spokesperson said that 'Jeb' was "chosen to represent the enthusiasm many on the Starliner engineering team have for the game, as well as the science, technology, engineering and mathematics (STEM) lessons it imparts to players."

Sequel

A sequel, ''Kerbal Space Program 2'', is to be released in early access on 24 February 2023.

See also

* Space flight simulation game
**List of space flight simulation games
* Planetarium software
*List of observatory software
*Apollo 11 in popular culture

References

External links

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